The Ultrastructural Effects of Sulfachloropyrazine on Toxoplasma gondii Tachyzoites

BACKGROUND: Toxoplasmosis is one of the most common parasitic infections of humans and other mammals. This study was aimed to understand the mechanism of action of veterinary medicine-sulfachloropyrazine (SPZ, 99.97%) against Toxoplasma gondii. METHODS: T. gondii tachyzoites were soaked in PBS (as a control) or SPZ (250 mg/mL) for 2 h at 37 °C. After being processed, any ultrastructural changes of the tachyzoites that had occurred were observed by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). RESULTS: The tachyzoites from control groups with a uniform size had a smooth surface and intact cell or nuclear membranes. In addition, an oval-shaped nucleus, conoids and micronemes were also observed. By contrast, many parasites from the SPZ-treated groups were detrimentally affected by the treatment. Some appeared to be of the vacuolization in their cytoplasm, with the substantial reduction in the number of dense granules and the blur of some organelles. CONCLUSION: The morphology and ultrastructure of tachyzoites can be affected significantly by SPZ, which might kill the parasite by inhibiting its energy metabolism, inducing apoptosis and damaging its structure. The study provides an experimental basis for further study on the mechanism of SPZ against T. gondii.